1. Field of the Invention
The present invention relates to a hydraulic seal system, including: an annular seal ring groove which is defined in one of mutually opposed peripheral surfaces of a shaft member and a housing surrounding the shaft member, the shaft member and the housing being relatively rotatably disposed, and a seal ring mounted in the seal ring groove to come into contact with the other of the peripheral surfaces of the shaft member and the housing, such that when the seal ring receives a hydraulic pressure mutually opposed sealing sides of the seal ring and the seal ring groove are brought into pressure contact with each other.
2. Description of the Prior Art
There is a known hydraulic seal system including a seal ring made of cast iron and having a sealing side which is formed into a convex curved surface with its radially central portion raised, and which is put into pressure contact with a flat sealing side of a seal ring groove by hydraulic pressure (see Japanese Utility Model Application Laid-open 122274/90).
In the above known system, the sealing side of the seal ring is in the form of a convex curved surface and hence, the contact of the sealing side of the seal ring with the sealing side of the seal ring groove appears to be smooth at first view. However, the seal ring is made of cast iron into a rigid member, and therefore, upon an increase in hydraulic pressure, the convex curved surface of the seal ring may bite into the sealing side of the seal ring groove to break down the oil film provided between the sealing sides, thereby accelerating the wearing of each sealing side due to a failure of lubrication and deteriorating the sealability and endurance.